The audio variometer : the paragliders' essential tool
Beginners, intermediate, advanced, competitors, tandem pilots : everyone wants to stay up in the air as long as possible (even acro pilots !).
This is the primary function of the variometer : to indicate the vertical speed (measured in meters per second for paragliding in Europe, in feet per minute in other parts of the world and for aviation).
This information of climb rate (positive values) helps the pilot to find thermals, and better lock down the core, but also to have a better “buoyancy” and have a better progression into the air mass in order to minimize the altitude loss, staying around the best possible climb rate.
Then, the sink rate (negative values) indicates vertical speed “towards the ground”. If it’s too high, then the conditions are not favorables and the pilot must move away to another area.
What are the benefits of flying with a variometer ?
For us, human beings, flying is not natural and we don’t have a dedicated sense to 3D motion. Once the visual landmark to the ground is lost, it’s very difficult to figure out if we climb or sink.
But, in my harness, I can feel when I enter or leave a thermal.
Indeed, our brain uses three senses in order to know if we are in motion or not : the inner ear, the proprioception, and the eyesight.
Then, the brain mixes with precision these 3 informations to know where we are located in the space, in which rotary movement, and at which acceleration.
Unfortunately, the “absolute” speed information is missing : it’s impossible to tell the speed of an airplane or a train if the window blind is down.
Worse, our senses can fool us, for example : when we are on a train at the railroad station and the train nearby leaves, we find ourselves disturbed, and our brain ends up having a hard time trying to figure out if we are actually moving or not until we check the other side, the still platform.
While we are in an established steady thermal, there is no more acceleration although we are still climbing, and if we are far from the terrain, hence without any visual landmark, it’s very difficult to figure out if we are inside the thermal or not (let alone in the core).
The variometer provides us this missing information and the response is immediate, we then know if we are climbing or sinking, and even the vertical speed of this climb !
If the paragliders could have a 4th natural sensor : altimeter / barometer in real time.
How does a variometer work ?
As previously seen, in order to be able to know its place in the space, the human body has three “natural sensors” :
- a gyroscope : the inner ear, which allows to follow the rotation (on 3 axis).
- an accelerometer : our skin in contact with the ground, the seat car, the harness, etc…, which allows to follow the accelerations (horizontal, vertical).
- a visual landmark : the eyesight, which connects to horizontal and vertical markers in order to give an absolute reference to the 2 senses above.
Unfortunately, one essential sense is missing to determine the altitude : a virtual vertical ruler graduated every meters for example.
That missing, but nonetheless present, information is the pressure. Indeed, the pressure is directly correlated to the altitude. Then, a pressure sensor allows to detect a decreasing pressure when the altitude increases.
Within the scope of a variometer for paragliding, the absolute altitude is not that interesting, this is the altitude variation that matters.
Then, by recording the pressure very frequently (minimum 50 times per second, to 100 or 200 times per second in the fastest cases), it’s possible, with an exclusive digital signal processing, to determine the altitude variation, in other words the vertical speed.
Is it possible to have a really instant variometer ?
Measuring only the pressure can struggle sometimes : it takes a pressure variation to measure a vertical speed, thus the result is always a bit late.
This is why an accelerometer sensor allows to measure the acceleration (entering a thermal) as quick as possible : this is the instant vario.
Of course, this sensor is extremely sensitive and requires an absolute reference : a gyroscopic correction is necessary.
This is an entire measurement chain (acceleration, rotation, pressure) measured more than 100 times per second with a specialized algorithm, that is performed inside the device, and allows to pass on to the pilot an information perfectly synchronized with his own senses. (remember : you have an accelerometer inside your head).
The Instant Vario Technology algorithm is exclusive at Stodeus.
It allows to combine all 3 sensors’ information : accelerometer, gyroscope, barometer. Then, the pilot gets a vario response right when entering the thermal, and not only after feeling the lift in the harness. Same for the thermal exit, which as important : the vario stops beeping immediately when the thermal ends.
In other words, the variometer beeps are totally linked with the pilot’s senses in his harness. Exit the 1 second delay between entering a thermal and the first beeps of the vario.
Sound modulations for more information
We need 100% of our visual field when flying, for safety reasons but also to stay aware at all the environment that helps us to find thermals.
The hearing sense is therefore much more available, because it is only used for few one-time information such as the wing crumpling, the relative wind’s variations, or a call on the radio.
Using a sound (a note) allows to convey an information, no sound means no information.
So by modulating the sound (vibratory frequency) in the range of KHz, it’s possible to convey an nearly infinite information.
In an audio variometer, beeps are made of three parameters :
- Frequency : pitch of the note (from deep to high-pitched sound).
- Cycle duration : time during which the note is played and its pause duration.
- Duty cycle : relation between the note played and the pause duration. For example, a duty cycle of 50% gives half of the time played and half of the time silent.
With an audio variometer, our hearing sense totally complements the three senses mentioned above, and allows us to instantly access to the precise information of our vertical motion.
From the competitors' point of view
“I can’t imagine flying my xc and vol-bivouacs without the sound of the vario. I have it set up so it’s very sensitive in the weak lift but then it flattens out in strong lift, if I’m going +7m/s I know I’m climbing, there is no reason to yell at me about it ! I like it when it reacts immediately, without delay, but sometimes I also fly with a delay and practice a different feeling, recognizing the lift before I can hear it. I also regularly turn off the vario and practice climbing without it. It’s easier close to the terrain and when there are other pilots around but sometimes, especially high or in weak lift, it’s practically impossible. Sound of the vario definitely makes our flying easier and takes all the focus from thermalling itself, gives us more time to plan to observe the terrain, the clouds, plan next crossing or just admire the views. There are solar, hassle-free options in a size and weight of a box of matches so why would I refuse to use one? After all there are not many sounds more delightful than the first bip after 20 minutes of scratching in some narrow gorge, the sound which then becomes more even and faster and faster ripping all the way to the cloud base.”
Kinga Masztalerz, Red Bull X-Alps athlete, vol-bivouac adventurer.
“At first, I struggled a bit with the immediateness of the response from this new genereation of variometers. With the old variometers, we were used to get confirmation of the entry into the thermal after feeling it, now we get the information at the same time. It’s kind of disturbing at first, but now it’s impossible for me to go back ! It’s super interesting to know immediately if you are actually really climbing or if at least you don’t sink too much, so you can react faster and perform better.”
Jacques Fournier (aka Grand Jack), international competitor.
Vario Tone Editor : the ultimate tool to fine-tune the vario of your leGPSBip / leGPSBip+
(open to all, even without leGPSBip / leGPSBip+)
The Vario Tone Editor will let you adjust the 3 sound’s parameters, graphically and intuitively :
As seen previously, there are 3 essential components :
The frequency curve :
The cycle duration curve :
The duty cycle curve :
How to shape the curves ?
It’s important to adapt the sound response type according to the climb / sink rate encountered and one’s flying level.
A linear response does not allow to fully use the abilities of our hearing sense. Furthermore, it’s way more interesting to have more information on small thermals of +0.5m/s rising slowly to +1m/s (100% gain) rather than a in a monster of +6m/s expanding to +7m/s (15% gain).
This is the reason why most of the variometers use a logarithmic curve (often of the 3 parameters, with slight variations).
The vario Tone Editor allows not only to modify these 3 parameters, but also to define different response types :
Fast response (example) :
Dampened response (example) :
The sink alarm
Both feared and strongly hated, this function allows the pilot to detect a sink rate higher than the nominal sink rate of his wing (between -0.8m/s and -1.7m/s for a standard wing).
The goal is to notify the pilot that he is located in an air mass highly descending that will make him sink a lot until he will be quickly forced to land if he stays in that area for too long.
It’s the pilot’s responsibility to set the appropriate threshold according to his flying level and capacity to handle such information while flying.
Overall, a beginner pilot will tend to simply disable this feature because it can be a tad stressful, an intermediate pilot might want to set a sink alarm at around -3m/s, and generally, an advanced competitor might have a preference for a -2m/s threshold, even if the sink alarm goes off as soon as he leaves the thermal.
The weak lift detector, or near-thermal tone
This indication tone is made of short “clicks” indicating weak lift (between -30cm/s and the pilot’s positive lift threshold, (default is +20cm/s), not strong enough to thermal but helping him to find thermal standing nearby.
On the image, the grey pilot doesn’t have his weak lift detector activated, while the green pilot has it activated. The near-thermal tone sounds when the pilot flies through weak lift, informing him that he is approaching a weak lift area, not optimum yet, but allowing him to search for a potential thermal core nearby.
The sound volume
Variometers are, or should be, always customizable with at least 3 volumes, in order to best adapt the volume according to the use case.
When the variometer is located on the helmet, in tandem for example, the volume minimum is discreet and does not disturb the passenger.
With an advanced wing, or with a noisy helmet in relative wind, the volume medium will be used.
Finally, on the cockpit, in the lying position of a full race harness, with a full helmet, the volume maximum is needed.
leGPSBip+ volume (as well as all other STODEUS instruments) can very easily be changed according to those three levels thanks to its side button, even while flying.
Are there other ways to pass on that information ?
Other non-visual technologies are possibles, such as vibrations for example.
But vibrations, and even more, modulations in the vibrations, are much more difficult to detect. It’s not possible to convey as much information through vibrations as all the one transmitted by sound.
Also, they can very easily be interfered. For example, missed calls on the smartphone in vibrating mode while walking.
Finally, this is a power-hungry technology : it needs enough power to shake a mass (device, hand, body), while the sound is a vibration of the air (indeed, much lighter).
The pilot is solely liable for the safety of his flights, this article cannot, in any way, engage STODEUS liability. It’s the pilot’s responsibility to set up the appropriate parameters according to his flying level and capacity to handle such information while flying.